What is the flickering thing in the hotel?

There is a red light flashing on the ceiling of the hotel room, which is a smoke detector set by the fire alarm system. It is used to prevent fire. You can relax, because the hotel room is a private space, and the hotel is not allowed to install probes. If the smoke in the room is too large, the smoke detector will give an alarm, and when the room will catch fire, the fire sprinkler will automatically start sprinkling water to extinguish the fire, ensuring the safety of every customer.